Electric furnace control apparatus.



v J. A. SEEDE. ELECTRIC FURNACE CONTROL APPARATUS APPLICATION HLED JUNE 2], 1917- 1,253,732. Patented Jan. 15,1918.

'7 Invehtori John .7 f.$ee

and useful Improvements JOHN A. serum, or SCHENECTADY, NEW YORK, ASSIGHOB TO I GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC FURNACE CONTROL APPARATUS.

To all whom. it may concern: r

Be it known that I, JOHN A. SEEDE, a citi zen of the United States,'residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new in Electric Furnace Control Apparatus, of which the following is a specification.

The present invention relates to electric control apparatus for electric furnaces, particularly for are furnaces. The object of my invention isto provide means whereby the length of the arcs and current flowing in the arcs may be maintained uniform. In my U. S. Patent #1206503 of November 28, 1916, is described an electric furnace control apparatus whereby motors connected to the electrodes are actuated by electrical switching means responsive to variations of current, or other electrical conditions of'the energy supply circuit. 7

In accordance wlth my present invention certain advantages herelnafter specifically explained are'secured by regulating one arc of a furnace in accordance with current variations, and regulatinganother arc in thesame circuit in accordance with voltage variations.

Referring to the drawing, the furnace is diagrammatically indicated by a rectangle 1, shown in dotted outline, and comprises a.

stationary conductor or electrode 2 located at the 'base of the furnace, and movable electrodes .3, 3 adapted to support arcs in series in conjunction with the stationary electrode 2. These electrodes may either all consist of carbon or graphite, or in some cases, the conductor 2 may be a charge of metal or other'conductive material in the furnace. A

motor 4 is mechanically connected to the electrode 3 by any form of suitable gearing, the drawing showing a speed reducing gear 5 driven by the motor acting on a nut 6 on the screw threaded rod 7 to raise andlower the electrode. The motor connected to the trode is shown as connected to a =gearing 8 and it is to be understood'thatthis gearing is connected to a motor and its control apparatus similarly to the motor and control apparatus shown in connection with elec trode 3.

The electrodes 3 and 3' are connected respectively to electric mains 9 and 10 receiv- 5 ing electric energy from'thesecondary of a tween the electrodes 2 and3.

Specification of Letters Patent. Patented J an, 15, 1918, Application filed June 21, 1917. Serial No. 176,218.

transformer 11. A relay magnet 12 is connected to the secondary of a current transformer 13, the primary of which is constituted by a portion of the conductor 9. The armature 1 4 of the relay 12 is connected to a lever 15 operating to make contact with either conductors 16 or 17 to complete a separate cincuit and thereby to energize either of relay magnets 18 and 19, as will be hereinafterdescribed 'in greater detail. These magnets in turn control the armature circuit of the'motor 4 to raise or lower the electrodes in order to maintain the current in an are between the electrodes 3 and 2 substantially constant. The winding of a second relay 20 is connected respectively to the conductor 10, which supplies the electrode 3 and to a conductor 21 which is connected to the electrode 2, thus being responsive to voltage variations of an are operating be- An adjustable resistance 22 in circuit with the winding of the relay 2Q-permits the setting of the magnet to be made as'desired. The armature 23 of the relay 20 is connected'to a switch lever 24, adapted to contact with either ofthe conductors 25 or 26 connected to a set of relays and contact-01's controlling the motor (not their'operation then continues automatically.

When the furnace is energized the relay 27' pulls up its armature and causes the switchlever 28-to complete a circuit between the conductors 29 and 80. In case the energy supply is interrupted the contactor27 releases and opens the circuit to safeguard the apparatus against injury.

In case the current in an are between the f electrodes 3 and 2 is too low the current-responsive magnet 12 completes a. circuit from the conductors 31, 32, which are preferably supplied with direct current to energize the relay magnet 19, the circuit being through the conductors 29, 30, switch lever 15, com ductors 16 and 33. The magnet 19 pulls up its armature 3 f, closes contact 35 and 36, and

energizes the motor 4, the motor circuit being through the conductor 37, resistance. 38,

contact 35, conductor 39, the armature of the motor, conductors 40,41, contact '36, and the conductor 33. The motor is connected to thereupon lower the electrode 3, thereby increasing the current until thefcontactor 15 releases and breaks the circuit of the magnet 19.

As the two arcs are in series, the current will increase between the electrodes 3 and 2, as well as between the electrodes 3 and 2 and if the former electrodes are too far apart, the voltage drop between them will be too great, and the voltage-responsive relay 20 will be energized to contact with the conductor 26 and set into operation a motor (not shown) to lower the electrode 3 the control apparatus being like the apparatus energized by the current-responsive contactor 12 child being omitted tov simplify the drawing. The reverse operation when, for example, the current'is too great, will cause the electrodes to be raised. I

In that case, the armature 14 of the magnet 12 is pulled down causing the switch lever' 15 to contact with the conductor 17 completing a circuit through the relay mag net 18, by way of conductors 42 and 33. The motor 4 is thereupon energized to revolve in the opposite direction to raise the electrodes, the circuit being by way of the conductors 33, 42, contact 43, conductors 43,- 39,

40, contact 44, conductor 45, resistances 46 and 38 and the conductor 37.

When the electrodes have been raised or lowered to a point which results in a change of current or voltage causing the contactor to open the motor is brought to a stop by dynamic braking in the following manner.

The counter-.electromotive force of the motor energizes a magnet 47 connected across the conductors, and by the closure of the contact 48, assisted by the spring 49;:inserts a resistance 50 in the armature circuit to quickly bring the motor to rest, as well understood'. While the motor circuit is closed through the resistance 50, a mechanical in-- terlock 51 prevents the closure ofthe relay magnets 18 and 19, which are attached respectively to interlocks 52 and p at I claim as new and desire to secure by Letters Patent of the United States, is

1. The combination of a plurality of electrodes adapted to support a plurality of arcs, electrical connections therefor, means.

I, supply conductors connected to said electrodes, means for controlling a motor connected to one electrode in response to current changes in the supply circuit of the corresponding electrode to move said electrode in a directlon whereby a desired current value is maintained, means for controlling a motor. connected to another electrode in response to voltage changes across an arc supported by said electrode to move said electrode in a direction whereby-a desired voltage drop is maintained, and means for brakmg said motors when the desired regulation has been attained.

In witness whereof, I have hereunto set my hand this 20th day of June, 1917.

- 4 JOHN A. SEEDE. 

